IT8148693A1 - Process for manufacturing offset printing cylinders - Google Patents

Description

DOCUMENTATION

RELIEF

'?Process for the manufacture of offset printing cylinders

SUMMARY < . The object of the invention is a process oOc ioQ >?? for the manufacture of offset printing cylinders a- CK < I ?.-having locking members positioned in spaces IV provided in the cylinders by means of a system ? Z

< cv NI

_in two pieces involving the adhesion of a compressible printing element OC <CQ to the cylinder with at least one edge C71 extending into the interspace of the clamping member, finishing of the edge extending into the interspace of the clamping member and subsequently the application under tension of a non-compressible printing element carrying the working surface receiving the printing ink indicia in a taut condition on the compressible printing element and the fixing of the ends of the non-compressible printing element

!compressible in the locking member under tension. The two-piece system implies the separation

?of the relatively thin compressible portion of the offset printing blanket cylinder from the relatively thinner ink transfer surface of the offset printing blanket cylinder. Furthermore,

a separate embodiment with pressure sensitive adhesive that secures the two-piece system together and not limited to the cylinders

< offset printing, to the product and the related process ? t/i < rment. ? ?- C .

C' DESCRIPTION c

i i The present invention relates to a

convenient manufacturing or coating of cylinders

-f .offset printing. Offset printing is also called

fsl Ci lithographic printing. The invention in certain aspects fi)

?? it extends to two-piece print elements in general.

In the past, rubber cylinders? for printing

Were offset cylinders made as rubber cylinders?

one-piece printing having a robust, dimensionally stable sublamina-00]LtOMA/v na or a plurality of

laminae covered with iine or more compressible laminae

covered with a further strong dimensionally stable foil which in turn was covered with

an ink transfer foil. A form

of making such a rubber cylinder?

Offset printing is illustrated in figure 2 as a technique

ca previous. An edge portion of the offset printing cylinder 10 is shown on the inside of the clamping gap 11. The blanket element is shown extending into the gap to a clamping mechanism (not shown) which holds the blanket element taut across the cylindrical surface 12 of the offset printing cylinder 10. The blanket element, as shown, has a

a substantially inextensible woven cotton fabric 13 cylinder sheet having a nominal thickness of 13 thousandths of an inch, or 330 microns, covered with an adhesive laminate of neoi? "

?prene 14 which has a nominal thickness of 1 mil- fi i

1/100th of an inch, equal to 25 microns, which in turn is covered by another layer 15 of cotton fabric.

?a substantially inextensible woven fabric, which also nominally has a thickness of 13 thousandths of an inch, equal to 330 microns, covered by a

1 adhesive layer of nitrile 16 which also has no? OMASJLp. !minally a thickness of 1 thousandth of an inch, equal to 25 microns, covered by a compressive layer-\

,mibile 17 having a nominal thickness of 25 mils, equal to 635 microns, produced in accordance with U.S. Patent 3,147,698

which is now cited for reference. This -

i?

I

Is the compressible layer covered by another layer?

na 18 di_adieSJ^AO_ nitrile having a nominal thickness of 1 thousandth of an inch, equal to 25 microns,

which in turn is covered by a sheet 19 of

stretchable nylon fabric having a thickness no-^

'thread of 6 thousandths of an inch, equal to 150 microns, < ?r co iJLa which is covered with a layer of nitrile adhesive < ?22 aggressive towards nylon, having o l-J _

O

a nominal thickness of 1 thousandth of an inch, pa~ C O O

< M B 'ri to 25 microns, which in turn is covered by < L. -fSJ or ?; a working face for the ink transfer, or < stro, consisting of a more rigid sub-foil 20 ! Ni < m nominally 11 thousandths of an inch thick, equal to 279 microns, covered by the

!

?ink transfer face 21 which is also nominally 11 thousandths of an inch thick. The total thickness of the rubber element ~

here? for offset printing of the illustrated embodiment is 82-83 thousandths of an inch, equal to

2.08 and 2.10 min and, as already established, it presents

|a one-piece structure. The thickness values

The indicated layers are nominal since each layer has a somewhat variable thickness. The described

rubber element? for offset printing is sold by W.R. Grace & Co., under the name of elements

blankets? for 3-print offset newspapers PCLT.VEE (trade name of W.E. Grace <? Co,,) IIP A'eb.

Since each end of the offset printing blanket must be fixed in the clamping gap of the offset printing cylinder, the gap in the circumference of the cylinders must be between 1/4 and 3/4 inch wide.

the ce (equal to 6.35 and 19 mm) since each end of the rubber element when it enters the gap

It is 82 thousandths of an inch, or 2.08 mm, and the ends generally contain bulky locking bars. The size of the bars can be reduced commensurate with the reduced thickness and reduced volume of the rubber element portion.

which is fixed in the said interspace, as will be obvious to those skilled in this art. If the rubber element could be thinned at the point where it enters the interspace, the interspace could be made narrower, and this would increase the number of printing lines that a cylinder of a given circumference could accommodate. The area

A cylinder circumference occupied by the gap will not accommodate the print lines. The question is how to achieve this goal.

in such a way as to allow for long continuous periods

to function slowly and yet maintain a print of

high quality such as that required in the

offset printing.

The rubber elements with double filling

pieces have been known for many years in the art of

newspaper printing and printing technology

DILITHO*. These two-piece rubber elements ?a.

</< are not involved in the transfer of the in <

5 O you say of printing on the paper but instead are involved Oc Qo to provide a cushion behind the paper when the typeface is pushed against the Ni OQ paper from the opposite side. Therefore, of course, none of them presents the working surface for the

ink transfer. In other respects - the detail of their actual construction, they

are they still very similar to the rubber element?

two-piece offset printing of the present invention.

In fact the bottom or compressible layer

of example 1 of this patent application,

which shows the present invention, is identical for

physical structure to the structure provided by W.R.

Grace & Co. as rubber sheet? for clothing

Polyfibron* NY type printing presses for the appli-* Trademarks of ATiPA Research respectively

and of V/.R. Grace.

Nyloprint* typographical printing, illustrated in Figure 3. It consists of a removable polyethylene release sheet 25 with a layer 26 of pressure-sensitive adhesive, nominally

.a thickness of 2 thousandths of an inch, equal to _50_ _ _ jnicron, a sheet 27 per cylinder of substantially inextensible woven cotton fabric, for e-_ <| -4 'j _ ? ? . . " . '? . ; V 1example that previously described but having_ !_^ _ . . .

?a minimum thickness^ of only 12 thousandths of ^ ? O

.inch, equal to 305 microns, covered with an adhesive- Q

I <t . ? Z ? nitrile rubber 28 having a nominal thickness of 2 thousandths of an inch, equal to 50 microns, covered by a compressible layer 29 of the same description as previously indicated and having a _

!

nominal thickness of 25 thousandths of an inch, equal to

635 microns. The compressible layer 29 is covered with a stabilizing thermosol layer 30 which has1

;a nominal thickness of 9 thousandths of an inch, equal to 228 microns. I In letterpress printing, the covering element of the two-piece clothing sheet

1? called a "drawsheet". A typical drawsheet

!? Sold by W.R. Grace & Co. under the name of POLYDRAW* newspaper printing press blanket. Such a drawsheet is shown in the Factory Prints of BASE and W.R. Grace.

figure 4._The drawsh.eet illustrated in figure 4 has a thickness of 33 thousandths of an inch, equal to

at 0.84 mm, and is constructed with a fabric sheet of_

stabilizing cotton 31^as previously described, which has a nominal thickness ^

_di__l5_m?jl-ths of an inch, p?rija 381 microns, the

j

which is covered with a sheet of adhesive 32_nii

trilico which is aggressive towards cotton fabric and nominally has a thickness of 0 l*J ?OS?{-. . . ~

1 thousandth of an inch, covered with a sheet of 33-grade nitrile OoS-??os--3-sive adhesive which is aggressive towards 2 --?-i<srr-IV nylon and has a nominal thickness of half a mil- o? ?-?

2 tN lth of an inch, equal to 12.7 microns, covered with

< a smooth, uniformly woven nylon fabric 34 > CO

X? c having a nominal thickness of 4 thousandths of an inch, equal to 100 microns woven with nylon multifilament yarns having a denier count of 70,

with 100 threads in the warp direction and 90 threads

in the weft direction. The nylon sheet is

covered with another sheet of nitrile adhesive

35 which is aggressive towards nylon and has a nominal thickness of half a thousandth of

;inch, equal to 12.7 microns, and this in turn ;

:it is covered with a 36-sided layer of rubber

which has a nominal thickness of ?9 thousandths of poi-

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thickness, equal to 228 microns, and is not suitable for transfer surface but instead is suitable for use to reinforce the paper that is printed on its exposed surface.

An object of the present invention is to provide a process for manufacturing offset printing cylinders which makes it possible to reduce the cylinder clamping gap, thereby increasing the number of printing lines or rows that a cylinder having a given circumference can accommodate.

A further object is to provide a process for manufacturing offset printing cylinders which improves the quality of printing. Yet another object of the invention is to provide an offset printing blanket which satisfies both of the above-mentioned objects.

SUMMARY OF THE INVENTION

The subject of the invention is a process for manufacturing an offset printing cylinder having a clamping gap. The process consists of adhering a compressible printing element of one-piece construction to the cylinder, extending from one edge of the clamping gap to beyond the opposite edge of the clamping gap.

locking. The portion of the compressible printing element that extends beyond the edge of the locking gap is trimmed so that it is substantially flush with the edge of the locking gap. Thus, a

print carrying a receptive work surface

< in relation to printing ink indices

Q?r ?non-compressible is stretched on the printing element? Or pa compressible and its ends are fixed

Ni under tension in the locking gap. Prefe -?

remarkably, the compressible printing element is ?. ? ?? ? ?? Or made to adhere to the cylinder by means of an adhesive. ??

?

0? - - - - In another aspect of the invention, there is provided a method for securing an element.

_ _of.a.cylinder.printing,.in.a.more.general.sense.The

...process consists of attaching a compressible printing element to a cylinder simply by using a layer of pressure-sensitive adhesive between their interfacing surfaces, coating the compressible printing element with an ejector,

...non-compressible printing element and attaching it to the compressible printing element simply, me-,

_diante .1 'using a pressure-sensitive adhesive^

and in fixing the ends of the printing element

non-compressible._in_the_cylinder.._

The process consists of fixing the non-compressible printing element directly to the compressible printing element at their interfacing surfaces by means of a pressure-sensitive adhesive forming a layer between them, no other intermediate structure being present between the non-compressible printing element and the compressible printing element.

Cn ' -T Still under another aspect of the present invention, a printing element is provided i?l ?s.

->?> ! *3 -1q.ualP comprises a compressible printing element -Q ? i < ? T" .having a pressure-sensitive adhesive on one face thereof, a substantially non-extensible lamina adjacent to said pressure-sensitive adhesive and a compressible lamina covering the substantially non-extensible lamina; and a

non-compressible print that features an adhesive

'sensitive to pressure on one side of the joint

1to the compressible printing element, a substantially non-extensible foil adjacent to the second

!pressure-sensitive adhesive and a thin, external working foil covering the second, substantially non-stretchable foil.

i

_ P.refer.ably,.1_*print-element.,pre-

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includes an external work surface plate which is a work surface that receives and transfers the printing ink and a plate of hardened stabilizing material provided in the compressible printing element to cover the compressible plate.

PREFERRED FORMS OF REALIZATION

. . FIG. 1 is a partial sectional view through a composite offset printing cylinder constructed in accordance with the present invention, the partial sectional view being taken at the edge of the clamping gap; ..

Figure 2 is a partial sectional view, similar to that of Figure 1, of.... an offset printing cylinder made from a single piece of the prior art printing blanket; ... __ .. _.

_ . . _ Figure 3 represents a partial sectional view of the undergarment sheet for _ .a letterpress printing machine;

Figure 4 shows a partial sectional view of the drawsheet for the typographic printing press.

Considering now Figure 1, an offset printing cylinder constructed according to the present invention is represented in a currently preferred embodiment. For the execution of the manufacturing process of the offset cylinder having a locking arrangement, the procedure which will be indicated below is carried out. The locking mechanism itself does not represent an element of the present invention and therefore does not

!? represented. For the same reason, the ends OOC of the printing blanket suitable for fitting to the particular locking device \?to are not represented since they can be formed in note ,Q ' I 2? ';

< manner. M Ci_ < CO

The offset cylinder 40 of FIG. 1 is constructed in accordance with the present invention by first adhering a compressible printing element of one-piece construction around the cylinder. For ease of assembly, the compressible element is adhered to the cylinder so as to extend from at least one edge of the clamping gap to

;beyond the opposite edge of the locking gap. The edge now extending beyond the edge of the locking gap is then trimmed . . . . . ? " Finished substantially flush with the edge of the locking gap in the position illustrated in FIG. 1 for the compressible member 43.

Preferably, the print element that

brings the work surface receptive to

of the inked indices of non-compressible printing

It is kept thin commensurate with convenient ink transfer performance

to the inked indexes and to the surface of the paper <3 cL c? which is printed on it and with sufficient mechanical resistance for long-term operation. The thickness pre-cut is between 10 and 50 thousandths of an inch, equal to L?'

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254 microns and 1,257 microns, respectively, more pre- fs.

?? " ?

preferably a thickness between 20 and 35 thousandths of O < inch, equal to 500 and 890 microns. ' M OS

< co The thickness of the compressible printing element is largely determined by three requirements.

First, it must be compressible enough to absorb irregularities in height.

of the surface that is being used. Secondly-_

^go, it must be thick enough to carry the ink transfer surface,

of the incompressible layer at the appropriate height:

Third, it must absorb the increase in thickness during deformations when the paper breaks and multiple layers wrap around the cylinder. The compressible element also helps absorb the pressure shock.

When the gaps between the rubber sheet and the rubber sheet and between the rubber sheet and the plate meet, the pressure in the passage gap decreases to zero. This is also referred to as roll rebound, which causes striations.

d. across the width of the printing press, c/i <w* Of course, it must have sufficient strength and integrity to maintain the integrity of its structure over extended periods of use. Therefore, it is preferable to reinforce the outer surface with a tough, resilient rubber or plasti-tfai < ca. The preferred thickness for the printing element?

?t compressible ? between about 20 thousandths of an inch, equal to 500 microns, and about 150 thousandths of an inch, equal to 3?81 mm, preferably between about

30 mils, or 760 microns, and about 130 mils, or 3.3 mm. It is also important that the compressible printing element have sufficient compressible depth or compressible unit thickness to perform adequately. The thickness of the compressible unit is preferably between about 10 and about 100 mils, or 250 microns, or 2.5 mm, more preferably between about 20 and about 80 mils.

It is preferable to assemble the element of.

pa_.compressible on the offset printing cylinder facen-

do.ader?re_ljelemento al.cilindro with a pre- adhesive

feels, on the printing element. Other procedures_

to_make_the_compressible_print_element stick_<

- d t/> on the offset printing cylinder could include the use of hot melt adhesives or o ??J i o

1 mechanical organs that pierce the face of the ele-_ to. 3

&

; compressible print chin entering commitment <z % !

? with the cylinder ?

ts?? <? A feature of the present inven- ' N3

C2

<r tion ? constituted by the fact that the stamp cylinder d?

?~c~ ?

: pa offset composite.pub be_made to work fi- _

i

no a._qusindq_the 'non-compressible print' element

i

; it is damaged and then it can be replaced?-

[_to without disturbing the print element compress-^

!

The bile. The non-compressible printing element is damaged.

! is released from the locking group and

?

_a new non-compressible element is stretched on the-

I the undisturbed compressible printing element and

! is fixed through its ends in the inter-1 ;

t locking space. <

_ Furthermore .11compressible .printing .element-_

it.can also be..separated from.the.printing cylinders.

offset by separating the pressure-sensitive adhesive from the cylinder and can then be replaced in the manner previously described and the non-compressible printing element that was released by such removal can be replaced all in the manner already described above. Naturally, both ^ l l/l;.these parts can be replaced in the same <

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time

c 1 t As used in this description, the term offset or offset printing indicates a quality

It is a printing process that involves receiving ink from a plate by means of an intermediate organ, an offset blanket, which transfers the ink to the paper or other substrate to be printed. In its preferred form, it is

jcomes directed to the cylindrical offset printing medium

having some form of means of securing the ends of the rubber sheet or locking;

i

The present invention is further illustrated by the following example.

I

? EXAMPLE

,_ _ . Referring to Figure 1, a two-piece offset printing blanket sheet 42 according to the present invention is shown assembled

on an offset printing cylinder 40 having an inter-I

!print space 41 and an external circumferential surface.

A 43 in compressible printing element

a single piece is made to adhere directly to the

:cylindrical surface 44 of the offset printing cylinder

40 through the use of a layer 45 of adhesive sen- .

< jsible to pressure. It will be understood that a release sheet (not shown) such as the one represented in 5 .

0_JAJ__ felt in the previous technique with the number of ri O ?? Ci.

Pi O injury 25 in figure 3> ? initially present fi: ?

^ co to cover the pressure-sensitive adhesive. The oo ?

^fvL^O' V N?? The release sheet is naturally removed to **? cv ? 5rst oc !allow the coro- C<Q ai primible printing element to adhere to the print cylinder. The pressure-sensitive adhesive has a nominal thickness of 2

i

thousandths of an inch, equal to approximately 50 microns.

-_A_sheet_with_a_46_cylinder_overlaps_the_a- _

-The pressure-sensitive adhesive provides resistance.

j

? za-mechanica.e.stability?_against_stretching_.in .senr

I know...longitudinal, and .in ..lateral.direction.._The .sheet?of_

.ei1indno_?_made.of_a_low_stretch_cotton_fabric.having.high_mechanical_resistance.and.with.a_nominal_height_of_12_mill.ths_of_

L-inch, approximately 4 microns. The cloth

The dro.is_.covered_with_a_sheet_of_ni-adhesive_48

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nitrile adhesive having a nominal thickness of 2 mils, or approximately 50 microns. The nitrile adhesive is overlaid with a compressible sheet 47 constructed in accordance with U.S. Patent No. 3,147,698. The nominal thickness of the compressible sheet is 25 mils, or approximately 635 microns. The nitrile adhesive serves to adhere the cylinder sheet to the compressible sheet and also provides additional thickness for the compressible printing member. The compressible layer 47 has a force-cured thermosol face coating or coating 49 to harden and stabilize that member and to provide a force-transfer-cured external surface in the nature of a hardened surface of high integrity. on the compressible printing element 43. The foil 49 has a nominal thickness of 9 mils, or 228 microns, and also provides thickness to the compressible printing element.

mobile 43.

The thermosol has the following composition: 60 parts dioctyl phthalate, 100 parts quality polyvinyl chloride resin available as [ . . .

dispersion (Geon 121, B.P. Goodrich), 25 parts of a phenolic resin (SP 6600, Schenectady Chemicals, Inc.), 15 parts of triethylolpropane trimethacrylate (Monsanto X980, Rohm and Haas), 3 parts of a barium/cadmium-zinc stabilizer (6V, 6A, Ferro Chemical Corp.);

0.3 parts 40% organic peroxide on an inert feed (Luperco 2313CL? Pennv/alt Corp.). The composition was prepared by charging the ingredients in the order listed in a mante-I reactor.

The composition is cured at 75°F (24°C) with stirring. After thorough mixing, which takes approximately 45 to 60 minutes, a thick liquid with a viscosity of approximately 20,000 to 30,000 cps is obtained. This composition is then applied as a blade hub coating to the compressible foil and cured at 340°F (171°C) for approximately 5 minutes.

The compressible member 43 is applied to the cylinder by lining an edge of one end with an edge of the gap 41 and leaving the opposite end extended into the gap from the opposite side of the gap.

Then, the portion of the end of the compressible element that extends into the gap is trimmed to the edge of the gap. The total thickness of the compressible printing element is 50 mils, or 1.27 mm.

The printing element 50 carrying the working surface that receives the inked indices

of non-compressible printing has a cylinder sheet or blanket 51 which has a similar structure to that of the blanket 46 of the compressible element and also has a nominal thickness of 15 thousandths of an inch, equal to 381 microns. The sheet 51 is covered with a layer 54 of nitrile adhesive having

of which a nominal thickness of 1 thousandth of an inch, equal to approximately 25 microns, which proves to be aggressive towards the cotton, which in turn is covered with a layer 53 of nitrile adhesive having:

?? < te a nominal thickness of 1 thousandth of an inch, .--to' equal to about 25 microns, which is aggressive towards nylon. The adhesive layer 53 is covered 2

and with a woven nylon fabric having the same structure as fabric 34 of the figure drawsheet

4 with a nominal thickness of 4 thousandths of an inch or approximately 100 microns. The nylon sheet is coated with a layer 58 of nylon-aggressive nitrile adhesive having a nominal thickness of 2 thousandths of an inch or approximately 50 microns, which in turn is covered by the working surface 55 for receiving and transferring the 5 inked indices, which consists of two layers 56 and 57 each of which has a nominal thickness of 5 thousandths of an inch or approximately 12 microns,

and has the same structure as the one-piece offset printing blanket sheet shown in the figure.

2.

The total thickness of the non-compressible offset printing element 50 is 33 thousandths of an inch, or 838 microns. This gives a thickness

total nominal of the offset printing blanket sheet?

in two pieces of 83 thousandths of an inch, equal to 2.1

mm.

The non-compressible printing element 50

is placed on top of the compressible printing element 43 and then stretched over it.

The ends of the non-compressible printing element are clamped in the clamping gap under tension.

. The composite offset printing cylinder was operated for a number of months.

test and the print quality is compared with the quality of an equivalent offset printing cylinder made from an offset printing blanket sheet in

one piece according to figure 2. The quality of the

print appears to the naked eye to be slightly higher with the cylinder made with the sheet

rubber? in two pieces of this example.

_ _ It is surprising to note that the two-piece offset printing blanket according to the present invention was also able to meet the quality requirements of the two-piece offset printing blanket.

a single piece collected_smaller than it It must be understood that the two-piece system has been tried at least twice in the previous years, but that

< the problems that have been encountered with the formation of folds and creases have been encountered Q ? ~ . ~ " " "*n??7 ? and such attempts have not been pursued. Also in the ? ^previous work on the present invention the problem of the formation of folds ? has been encountered. Si M SS

There is another preferred embodiment which is substantially identical to that of the K

listed in example 1, except that

T ? i

the non-compressible offset printing element is more

f

;thin. With this embodiment, the sheets

' of paper filling or clothing sheets of

* ; ? . . .

'paper blankets are placed between the compressible offset printing element and the non-compressible offset printing element to adjust the overall thickness of the two-piece offset printing blanket sheet to the exact desired thickness value. Such a com-T! :

! combination allows for greater flexibility

! possibility of variation during use. The rubber sheets

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what? of .scampa offset^in a _single piece^zzo that require_

sheets of paper clothing underneath them to increase their height are currently

sold by W.R. Grace & Co. In a specific embodiment of the two-piece rubber sheet,

the reduced thickness is provided by using a tes-. ' ~ . " 4

a. ;thinner cotton fabric at 51 of Figure 1, nominally 12 mils, or 304 ; O-UL . . or microns, rather than 15 mils, or 381 microns, the thinner adhesive layers 53?? z ?i'l_J a NJ < co 54 and 58, each of which nominally has a co ::

'? or thickness of half a thousandth of an inch, equal to approximately <

cc 12.7 microns, and the two receptive layers 56 and 57 for <

co of ink each have a nominal thickness- c i

king of 4 thousandths of an inch, equal to about 100 microns,

to provide a total thickness of the element of

non-compressible print nominally 25.5 thousandths of an inch, equal to 647 microns.

Another embodiment of the present invention which is preferred but not yet fully developed is the application of

!a pressure-sensitive adhesive on the surface

lower or on the internal or bottom surface 60

jdell?non-compressible offset printing element 50

:to stabilize its surface contact with

43. Those skilled in the art will understand that, prior to assembly, the pressure-sensitive adhesive would be covered with a release sheet which would be removed upon assembly. The use of the pressure-sensitive adhesive on the bottom surface of the non-compressible offset printing element will reduce the amount of force required to clamp the ends of the non-compressible offset printing element and secure it in place. The pressure-sensitive adhesive connecting the non-compressible offset printing element to the compressible offset printing element allows the non-compressible offset printing element to be separated and replaced without requiring replacement or separation of the compressible printing element from the offset printing cylinder. This aspect of the invention could also be applied to drawsheets used for apparel for securing to the underside of the apparel. Therefore, it could have applicability to any printing element for a printing press cylinder.

Furthermore, intermediate filling and/or compressible elements having pressure sensitive surfaces may be inserted between the described elements.

Claims (16)

1. A method of manufacturing an offset printing cylinder having a clamping member comprising adhering a compressible printing element in one piece to said cylinder extending from one edge of the clamping gap beyond the opposite edge of the clamping gap, trimming that portion of the compressible printing element extending beyond the edge of said clamping gap substantially flush with said edge of the clamping gap, unfolding a printing element carrying a working surface which receives and transfers non-compressible printing ink in a condition stretched over said compressible printing element and securing the ends in said clamping gap under tension. 2. Procedure for filing the claim 1, wherein said compressible printing element is-^ ~ ?? made to adhere to the said cylinder by means of an adhesive. _ _ _ ?_ _ ?.g??7 <t ?? i a O ; 3. A method according to claim 0 *1 " ? 2, wherein said compressible printing element pre-is! O or has an external surface which is hardened for?O . o < NJ transfer of force. CQ 4. The method of claim 1 wherein said printing element carrying the working surface receiving the non-compressible ink has a thickness of from about 10 to about 50 thousandths of an inch, equal to 254 microns and 1270 microns. 5. Process according to claim j4, wherein said compressible printing element has a compressible unit thickness of approximately -J; !10 and about 100 thousandths of an inch, equal to 254 and i ! i2540 microns. '1 6. A method according to claim 5, wherein said compressible printing element is made to adhere to the said cylinder by means of a pressure sensitive adhesive. 7. Process according to claim 6, wherein said compressible printing element has a compressible unit thickness of approximately d. c/i < 20 and approximately 80 thousandths of an inch, equal to 508 microns and 2.03 mm, and said non-compressible element has a thickness between approximately 20 and approximately 35 thousandths of inch, equal to 508 and 890 microns. 8. Process according to claim 1, wherein said composite offset printing cylinder is operated until said non-compressible printing element is damaged, said non-compressible printing element is released from said lock and a new printing element non-compressible print is stretched onto the element of compressible print undisturbed and fixed by means of its ends in said lock. 9. Procedure for fixing an element of printing on a cylinder consisting of fixing a compressible printing element to said cylinder simply by using a layer of pressure-sensitive adhesive between their surfaces interfacing, in covering said compressible print element with a non-compressible print element mibils and in securing it to said compressible printing element simply by the use of a pressure-sensitive adhesive which secures the ends of said non-compressible printing element to said ci- ?cylinder. ? -r r\ 10. The method of claim 9 wherein said non-compressible printing element is directly secured to said compressible printing element at their interfacing surfaces by means of said pressure sensitive adhesive forming a layer therebetween, no other intermediate structure being present between said non-compressible printing element and said compressible printing element. 11. A method according to claim 9, wherein said non-compressible printing element has on its external surface a working surface which receives the printing ink. 12. A printing element comprising a compressible printing element comprising a pressure-sensitive adhesive on one face thereof, a substantially non-extensible lamina adjacent to said pressure-sensitive adhesive, and a compressible lamina disposed covering said substantially non-extensible lamina; and a non-compressible printing element comprising a pressure-sensitive adhesive to the pressure on one of its faces connected to the said compressible printing element, a substantially non-extensible foil adjacent to said second pressure sensitive adhesive and a foil that forms an external work surface arranged in ? ? !knot to be covered - said second sheet substantially O LftJ .not extensible. 2og ? ? 13. A printing element according to claim 12, wherein said foil forming the super--: - *?.. 2 ? external work surface ? a work surface Ol ? 3? that receives and transfers the printing ink. oa 14. Printing element according to claim 12, wherein there is a stretchable fabric interwoven ;situated between said second substantially non-extensible plate and said external working surface. 15. The printing element of claim 12, wherein a sheet of hardened stabilizing material is provided in said printing element as priming so as to cover said compressible sheet. 16. A printing element according to claim 15 wherein said non-compressible printing element is directly attached to said element. of compressible printing in their internal surfaces .facing..by..the.said.second.pressure-sensitive.adhesive.which.forms.a.layer.between.them.O HJ tai t? < O n |no_?other_intermediate_structure.being_present_between_the_said_non-compressible_printing_element_and_the_said_compressible_printing_element_.